Rock drill rod

ABSTRACT

A rock drill rod which has a reduced diameter portion at either or both ends. The main portion of the rod is of constant diameter and threaded throughout its length. The reduced diameter portion is threaded substantially throughout its length. A drill bit is secured to the reduced diameter end and is dimensioned to drill a hole slightly larger than the diameter of the drill rod.

United States Patent 4/1941 Agostineto 175/394X 6/1941 Froome et al.... 175/323 6/1951 Miksis 285/390X l/l958 Van Note 175/394X FOREIGN PATENTS 2/1939 Germany 175/323 Primary Examiner-David H. Brown Attorneys-Carl R. l-lorten, David W. Tibbott and Frank H.

Thomason ABSTRACT: A rock drill rod which has a reduced diameter portion at either or both ends. The main portion of the rod is of constant diameter and threaded throughout its length. The

reduced diameter portion is threaded substantially throughout its length. A drill bit is secured to the reduced diameter end and is dimensioned to drill a hole slightly larger than the diameter of the drill rod.

I ROCK DRILL ROD BACKGROUND OF THE INVENTION This invention relates to rock drill rods and'a rock drill rod and drill bit system used in drilling small diameter holes; With respect to small diameter boreholes, theidrill rod is an improvement of the U.S. Fat. Application of LI. D'. Ditson and James F. Cantrel, Ser. No. 525,009, 'now US. Pat. No. 3.424,4 79,filedJan. 11,1968;

In modern drilling practices, there is anincreasinguse of long, small diameter holes.

One problem. encountered in drilling long;;small diameter holes is the lack of rigidity of the drill rod. As a percussive blow is delivered to the drill 'rod and asweight is applied to the drill rod, the rod bends. This bending which occurs results in an increase in stress in the rod and a crooked hole being drilled. r o

One method of overcoming this bending is to attach a centralizer to the drillingmachine. This addition can be expensive and is not practical in all drilling situations. Another method of reducing this bending is to make the drill rod more rigid. In general, the rigidity of the drill rod can best be increased by increasing the diameter of the rod..The rod must, of course, fol low the drill bit down the hole being drilled, and there mustbe sufficient clearance between the borewall and drill rod to permit cuttings to pass out of thehole. .The diameter of the drill rod is therefore limited bythe sizeof the holesbeing drilled.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The drill rod and drill rod and drill bit system of the present invention will be used in combination-with a drilling machine such as that generally indicated at l in FIG.- I. The drill rod 2 is connected to the drill'l in a manner well-known'in the art.

' The drill delivers an impactto the drill rod and rotates'the drill The threaded socket 'on the drill'bitswhich are used for v drilling smalldiameter holes istoosmallto permit adequate attachment of the bit to a conventional constant diameter rod bending of therod.

Prior drill rods which, have sufficient, rigidity to prevent bending while permittingthe attachment of small drill bits have the disadvantage-thatonce they, fail,-the rod has either lost its usefulness ormust be returned to the shop for reconditioning such as for. rethreading. A drill rod of this type is normally 10 or 12 feet long. If the' end of a conventional rod which permits attachment of a small hole bit is broken, the remaining length of the, rod cannot be used. Since this is where rod failure is most likely; to occur, use of prior drill rods which provide ample. rigidity yet permit small hole drilling are not economical,

1 SUMMARY whichis capable ofbeing reconditionedin the'field should failure occur.

It is still a further object of this invention to provide a drill rod which hasprolonged economic life.- I

In general, the foregoing and other objects will be carried out by providing a-drill rod comprising an elongated body having a first diameter portionanda-second, reduceddiameter portion at at least one end thereof and a bore axially. therethrough; said first diameterportion havingsan attachment thread extending substantially, the entire :length thereofya'n'd said second. reduced diameterportion having 'an attachment thread extendingfrom theend of the drill-rodtowardthe intersection of the first and second portions for a distance sufficient to permit a drill bit to be threadedly secured thereof.

BRIEF DESCRIPTION or THE DRAWING The invention will be described in connectionwith the annexed drawing wherein:

FIG. 1 is a plan viewof a drilling machine "employing one embodiment of thepresent invention vto drill ahole;

\ which is rigidenough to withstandithe' forces which cause rod. The impact is transferred to a drill bit 16 "to drill a hole 17 in rock or the like. The operation of the drill rod is well-known in the art and need not be described.

Referring to FIG. 2, the drill rod 2 includes an elongated body having a first portion 3 which extends for almostthe entire length of the drill rod. The first portion 3 is of substantially constant diameter throughout itsentire leng'thJThis portion is provided with a roll formed thread 4 which extends circumferentially around the drill rod throughout the length of the first portion 3 in the same manner asthe drill rodshown in US. 'Pat. Application Ser. No. 525.009. The thread 4 is characterized by a lubrication groove 5 which 'extendsthe length of the first portion 3. The end 6.of the rod is dimensioned to fit'the coupling on a conventional drilling machine.

A second', reduced diameter-portion 8 is provided at one end of the drill rod 2. A roll formed thread 9 is wound circum ferentially around the reduced diameter portion 8 from the end ll of the rod toward the first portion 3 of the drill rod. As with the thread 4, a grease groove 10 extends for the length of the thread 9. For'certain appli'cations'and methods of constructing the drill rod, it may be desirableto eliminate the grease grooves 5 and 10.

Because thethread 9 is roll formed, the reduced diameter portion 8 may be threaded all the way to the intersection of the first and-second portions. In order to more clearly show 7 the'separation between'the two portions 3 and 8. a space 12 on the reduceddia'mete'r' po'rt'i'on8 has beenshown without and couplings may be used. In certain applications, it maybe the strength of the rod. If the bore 15 were of constant'siz'e throughout the rodlength, the wall thickness of the reduced diameter'portion 8 would be reduced to the point ivherethe likelihood of rod failure at the portioni wou'ldbe greatly-im creased.

Thereduced diameter portionon'the efndof thefdrill rodj permits small diameter holes to be drillediwhile-insuring greater rigidityof thedrill rod. As shown in FIGFI, :a' drill liit 16 is threadedly secured to the reduced diameter'portionof the drill rod 2; The drill bit' 16 is 'dime'n'sionedto emanate I rod although such dimensions arenot intended to Bea-limiting factor. The threadedsoeket'on bit sfor drilling-smalldiameter holes will be necessarily small. The reduced diameterportion" '8 is smallenoughto permit 'the drill bit to be secured ther'e'to' while the largerdiameter portion 3 provides 'thenecessary rigidity. I

By way of example, the' first portion 3 ofth'e drillrodwill be 1 /zinches in diameter and thereduceddiameterportion'fi will be IAinches in diameter. Normally, a l "iinch'drill bit will be secured to the reduced diameter portion 8 although a bit as small as l Aainches may be used.

Although the length of the reduced diameter portion may vary from as long as more than half the overall length of the rod to as short as a few inches, it has been found that a maximum length of about 1 foot provides the optimum performance as far as rigidity and rod life are concerned. The reduced diameter portion is preferably threaded a distance at least twice the length necessary to attach a drill bit to the rod. The continuous threading of the reduced diameter portion 8 permits a broken end to be squared off and the drill bit reattached. Because the portion 3 of the drill rod is continuously threaded and the overall length of the rod is usually 10 or 12 feet, should the rod break so that the reduced diameter portion is no longer useful, an end of portion 3 of the rod may be squared off and a drill bit used for drilling larger diameter holes may be secured to the rod.

ln FIGS. 3 and 4, l have shown a modification of the drill rod of the present invention which is designed for drilling long holes of small diameter where it is necessary to use more than one drill rod. in order to provide rigidity, the rod has a first portion 21 which has a diameter sufficiently large to substantially reduce the tendency of the rod to bend. The portion 21 is provided with threads 22 and a grease groove 23 extending throughout its length. Reduced diameter portions 24 are provided at each end of the rod. Each is provided with threads 25 and a grease groove 26 extending substantially entirely from the end 27 to the intersection between the portions 21 and 24. A nonthreaded portion 28 is shown for clarity.

The reduced diameter portions 24 may be used for attaching a drill bit 16 to the drill rod or coupling two drill rods together as shown in FIG. 4. The coupling 30 may be of the type shown in the US. Pat. Application of J. D. Ditson and James F. Cantrel, Ser. No. 525,009. Use of a reduced diameter portion at the point where two rods are to be coupled together permits the use of a coupling having a diameter small enough to follow the drill rod down the hole.

As is the case with the embodiment of FIG. 1 and 2, the portions 24 are sufficiently long to permit reattachment of the drill bit or coupling should breakage occur. Continuous threading of the portion 21 permits the rod to be used for drilling larger diameter holes should the reduced diameter portions become useless. The lead I of the two threads 22 and 25 are substantially identical From the foregoing it is apparent that the objects of this invention have been carried out. The rod provides the rigidity lacking in prior art drill rods used in drilling small diameter holes. The continuous threading of the rod prolongs the useful life of the drill rod and permits field maintenance should breakage occur. The threads on both the large and small diameter portions are standard to permit the use of a standard drill bit and standard coupling. Although in the embodiment shown both threads are roll formed, in certain applications, it may be desirable to use some other method of forming on of the threads.

lclaim:

l. A drill rod comprising an elongated body having a first diameter portion and a second, reduced diameter portion at least one end thereof and a bore axially therethrough;

said first diameter having an attachment thread extending substantially the entire length thereof; and

said second, reduced diameter portion having an attachment thread extending from the end of the drill rod toward the intersection of the first and second portions for a distance sufficient to permit a drill bit to be threadedly secured thereto.

2. The drill rod of claim 1 wherein there is a reduced diameter portion at each end of the drill rod.

3. The drill rod of claim 1 wherein said bore is reduced in diameter at said second, reduced diameter portion.

4. A drill rod comprising an elongated body having a first diameter portion and a second, reduced diameter portion at least one end thereof and a bore axially therethrough;

said first diameter having portion attachment thread extending substantially the entire length thereof;

said second, reduced diameter portion having an attachment thread extending from the end of the drill rod toward the intersection of the first and second portions for a distance sufficient to permit a drill bit to be threadedly secured thereto; and wherein the lead of the thread on said first portion is substantially the same as the lead of the thread on said second portion and at least one of said threads is roll formed.

5. The drill rod of claim 4 wherein said second portion is threaded substantially completely to the intersection of said first and second portions and said second portion is no longer than one-tenth the length of the drill rod.

6. A rock drill rod and drill bit system comprising:

a drill rod having a first portion and a second. reduced diameter portion at one end thereof;

said first portion having an attachment thread which extends circumferentially around the first portion throughout its length;

said second, reduced diameter portion having an attachment thread which extends circumferentially around the second portion substantially completely throughout its length; and

a drill bit secured to the second portion of the drill rod and dimensioned to bore a hole having a diameter larger than the diameter of said first portion.

7. The drill rod and drill bit system of claim 6 wherein said drill bit is dimensioned to bore a hole at least one-eighth inch larger than the diameter of saidfirst portion.

8. The drill rod and drill bit system of claim 6 wherein said drill rod is provided with a bore axially therethrough and said bore is reduced in diameter at said second portion.

9. The drill rod and drill bit system of claim 8 wherein said second portion is threaded for a distance which is at least twice as long as the length of thread needed to secure said drill bit thereto.

10. A rock drill rod and drill bit system comprising:

a drill rod having a first portion and a second. reduced diameter portion at one end thereof;

said first portion having an attachment thread which extends circumferentially around the first portion throughout its length;

said second, reduced diameter portion having an attachment thread which extends circumferentially around the second portion substantially completely throughout its length;

a drill bit secured to the second portion of the drill rod and dimensioned to bore a hole having a diameter larger than the diameter of said first portion; and wherein the lead of the thread on said first portion is the same as the lead of the thread on said second portion.

11. The drill rod and drill bit system of claim 10 wherein both of said threads are roll formed.

12. A rock drill rod and drill bit system comprising:

a drill rod having a first portion and a second. reduced diameter portion at one end thereof;

said first portion having an attachment thread which extends circumferentially around the first portion throughout its length;

said second, reduced diameter portion having an attachment thread which extends circumferentially around the second portion substantially completely throughout its length;

a drill bit secured to the second portion of the drill rod and dimensioned to bore a hole having a diameter larger than the diameter of said first portion; wherein said drill bit is dimensioned to bore a hole at least one-eight larger than the diameter of said first portion; and wherein the lead of the thread on said first portion is the same as the lead of the thread on said second portion and at least one of said threads is roll formed. 

1. A drill rod comprising an elongated body having a first diameter portion and a second, reduced diameter portion at least one end thereof and a bore axially therethrough; said first diameter having an attachment thread extending substantially the entire length thereof; and said second, reduced diameter portion having an attachment thread extending from the end of the drill rod toward the intersection of the first and second portions for a distance sufficient to permit a drill bit to be threadedly secured thereto.
 2. The drill rod of claim 1 wherein there is a reduced diameter portion at each end of the drill rod.
 3. The drill rod of claim 1 wherein said bore is reduced in diameter at said second, reduced diameter portion.
 4. A drill rod comprising an elongated body having a first diameter portion and a second, reduced diameter portion at least one end thereof and a bore axially therethrough; said first diameter having portion attachment thread extending substantially the entire length thereof; said second, reduced diameter portion having an attachment thread extending from the end of the drill rod toward the intersection of the first and second portions for a distance sufficient to permit a drill bit to be threadedly secured thereto; and wherein the lead of the thread on said first portion is substantially the same as the lead of the thread on said second portion and at least one of said threads is roll formed.
 5. The drill rod of claim 4 wherein said second portion is threaded substantially completely to the intersection of said first and second portions and said second portion is no longer than one-tenth the length of the drill rod.
 6. A rock drill rod and drill bit system comprising: a drill rod having a first portion and a second, reduced diameter portion at one end thereof; said first portion having an attachment thread which extends circumferentially around the first portion throughout its length; said second, reduced diameter portion having an attachment thread which extends circumferentially around the second portion substantially completely throughout its length; and a drill bit secured to the second portion of the drill rod and dimensioned to bore a hole having a diameter larger than the diameter of said first portion.
 7. The drill rod and drill bit system of claim 6 wherein said drill bit is dimensioned to bore a hole at least one-eighth inch larger than the diameter of said first portion.
 8. The drill rod and drill bit system of claim 6 wherein said drill rod is provided with a bore axially therethrough and said bore is reduced in diameter at said second portion.
 9. The drill rod and drill bit system of claim 8 wherein said second portion is threaded for a distance which is at least twice as long as the length of thread needed to secure said drill bit thereto.
 10. A rock drill rod and drill bit system comprising: a drill rod having a first portion and a second, reduced diameter portion at one end thereof; said first portion having an attachment thread which extends circumferentially around the first portion throughout its length; said second, reduced diameter portion having an attachment thread which extends circumferentially around the second portion substantially completely throughout its length; a drill bit secured to the second portion of the drill rod and dimensioned to bore a hole having a diameter larger than the diameter of said first portion; and wherein the lead of the thread on said first portion is the same as the lead of the thread on said second portion.
 11. The drill rod and drill bit system Of claim 10 wherein both of said threads are roll formed.
 12. A rock drill rod and drill bit system comprising: a drill rod having a first portion and a second, reduced diameter portion at one end thereof; said first portion having an attachment thread which extends circumferentially around the first portion throughout its length; said second, reduced diameter portion having an attachment thread which extends circumferentially around the second portion substantially completely throughout its length; a drill bit secured to the second portion of the drill rod and dimensioned to bore a hole having a diameter larger than the diameter of said first portion; wherein said drill bit is dimensioned to bore a hole at least one-eight larger than the diameter of said first portion; and wherein the lead of the thread on said first portion is the same as the lead of the thread on said second portion and at least one of said threads is roll formed. 